The Quilter Sound Company was founded in 1968 by Patrick Howe Quilter. Patrick Quilter was an engineering student with an interest in electronics and music, who built his first amp in 1967 for a friend. In the early 1970s the company operated out of a store in Costa Mesa, California and the amplifiers were built and sold on the same site.
Over the years, the Quilter Sound Company became more focused on developing professional power amplifiers and the guitar amp side of the business became less important. In the 1990s Quilter developed network audio systems to control and monitor amplifier systems remotely and also moved into loudspeaker research and development. The company was renamed QSC, LLC in 2015.
Patrick Quilter retired from QSC in 2011, but then founded Quilter Labs to develop portable, solid-state, high-power guitar amplifiers.